DESCRIPTION: In 1999, 21 per 10,000 construction workers in Arizona sustained multiple injuries and of these, 32% missed 31 days or more from work as a result of a fall to a lower level. This study will examine the effectiveness of the preassembly of roof structural components in reducing costs and lost work time related to injuries and pain. A quasi-experimental design will be used to compare two methods of roof assembly, one from the ground (treatment), the other from an elevation (traditional/control). Hypotheses are: (1) Workers who participate in the treatment group will experience less strain and pain, fewer injuries, less lost workdays, and submit fewer worker compensation insurance claims than those who participate in the control group. (2) Workers who participate in the treatment group will have a fewer close calls than those who participate in the control group. (3) Costs associated with the treatment group will be less than costs associated with the control group. The Training Intervention Effectiveness Research (TIER) model will provide the evaluation framework for the study. Three framing trade companies (two treatment and one control) will participate in the study. The evaluation will include both a company level and worker level analysis. Eligible crews will be selected by the company Chief Officer. Within the crew, full time native English or Spanish speaking workers over the age of 18 are eligible to participate. Data will be collected using: (1) bi-weekly, less than 5-minute interviews, (2) observation, both in-person and through photography, (3) document review, and (4) visual analog and numerical rating pain scales. Qualitative data will be analyzed using componential analysis. Quantitative data will be analyzed using non-parametric and parametric tests as indicated by level of measurement and variance distributions. The modification of the roof assembly process, if proven effective, may serve as a form of safety intervention and may be better accepted both by employer and worker than other existing safety interventions (e.g. fall protection).